enum ERRNO
{
    USAGE_ERR,
    SOCKET_ERR,
    BIND_ERR,
    LISTEN_ERR,
    ACCEPT_ERR,
    READ_ERR,
    SEND_ERR,
    CONNECT_ERR,
    WRITE_ERR,
    PTHREAD_CREATE_ERR,
    SETSID_ERR,
};
